Ferrous metal ice tray



Patented Aug. 1945 reasons mrrAL ICE may- Albert L. Bunting, Deal-born, and Adam- '0.

Schultz, Detroit, were; said Schnlh assignorto said Bunting Nb Drawing. Application March 6, 1942,

Serial-No. 433,629

4 Claims. (Cl. 62-1085) The present invention relates to a novel ferrous metal ice tray having an improved corrosionresistant ornamental and protective coating.

Metallic trays and grids customarily wed in refrigerators for producing. ice cubes or other frozen substances are subjected in use to a wide variation in temperature andare used 'under conditions particularly conducive to surface corrosion. Such objects frequently are subjected to elevated temperatures on the exterior surfaces while ice or other frozen materials are in the pan. Also, such pans may be used for cooking or ,bakingand are subjected to considerable handling. The surfacesthereof also are subjected to much wear and abrasion, particularly when used with grids adapted to free the frozen for use in connection with such objects since these metals do not rust or corrode under the conditions of use. Since the materials frozen or prepared in'such objects normally comprise food or other substances intended for human consumption, it is essential that any coating applied thereto must be non-toxic in character, and be.

'freefrom materials which taint or impair the taste of the food frozen or prepared therein.

Protective coatings suggested heretofore for material therefrom by -mechanically appl ed ducing other deleterious effects, thus permitting a rubbergridorinserttobesafelyandsaiisfac torily employed in connection with a steel or ferrous metal tray, if desired.

A further objectof the invention is to provide a coating for an ice tray or grid to which frozen materials, such as ice, do not adhere very firmly, and thus to provide a tray and grid from which icecubesor the like mayhereadilyremoved.

Still a further object of the invention is to provide a protective coating on an ice tray which consists of a'hard; tough, relatively flexible film or layer which fills irregularities in the metal surfaces to produce a smooth surfaced product, such coating being pleasing in appearance and being white or colored as desired.

Other objects and advantages of this invention will appear in the following description and appended claims. Before explaining in detail the present invention it is to he understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation, and it is not intended to limit the inven? tion beyond the requirements of the prior art In order to apply the present protective coat-. ing to ferrous metal objects. it is desirable to clean the surfaces to be coated.

use with steel or other ferrous metal objects have been defective in one or more of the foregoing respects and therefore have been unsatisfactory for use with steel or ferrous metal ice trays or grids.

Accordingly, it is one object of the present invent on to provide a coating for a steel or ferrous metal ice tray or grid which fulfills the aforesaid requirements for such a coating, and which therefore effectively and satisfactorily protects the tray and grid from rusting or corrosion despite the wide temperature ranges to whichthese articles are normally subjected, and despite the:

handling, wear and abrasion to which they are .al o normally subjected.

Another'object of this invention is to-provide For example-steel refrigerator ice trays are normally fabricated froma sheet of steel by drawing or stamping operations. Accordingly,"

said trays usually possess oil on, their surfaces,

as well as dirt and other foreign substances. To

clean these surfaces we prefer to use an emulsion type cleaner such a triethanol amine soaps. The latter comprise triethanol amine as an emulsifying agent, water, and a. suitable fat or oil containing fatty acids, such as oleic acid, stearic cleaners may be used including solvents for the oil or grease normally found on the: surfaces of the aforesaid objects. Among such solvents are benzene, naphtha, gasoline or mixtlfir stabilized trichlorethylene, carbon tetrachloride, and perchlorethylene,

Another object r the invention is to provide a protective coating whichmay be used with rub- In connectionwith the cleaning operation,-it

is also recommen ed that the water used to form the'emulsion be'carefully'checked for hardness and, in generaLbe-checked' for impurities con tained therein. If necessary, thiswater should be conditioned, that is, it should be softened or es thereof,

treated to remove impurities, if deleterious, or treated to render said impurities-harmless. We have found it is preferable that the water should have a pH value of approximately 8. The pH value may be varied in many waters by the use of relatively small amounts of sodium metasilicate, sodium phosphate and with phosphoric acid. It will be understood that water softening or conditioning is wellunderstood by chemists familiar with this subject and that one skilled in the art may take suitable steps to provide the proper water to insure an effective emulsion type cleaner. It will also be understood that this 1 emulsion type cleaner may be utilized in any of the various ways, that is, the object to becleaned may be submerged in the cleaner, sprayed therewith, etc., preferably at elevated temperatures such as approximately 160 F. to approximately 180 F.

After the objects have been subjected to the cleaning operation, we have found it desirable to rinse them in order to remove the cleaning solution from the surfaces. For this rinsing operation we have found that hot water is effective. Also after the cleaning and rinsing operation,

of carrying out the foregoing sub-coating operation, the refrigerator tray, or other ferrous metal object treated, will be provided with a rust resistant coating consisting essentially of ferrous phosphates or chromates which cover the surfaces of the object. However, this coating is not suflicient in itself to protect the object from rusting or corrosion when it is subjected to handling,

abrasion, wear and relatively great temperature changes to which a refrigerator tray, for instance, is subjected. Accordingly, in practicing the present invention an additional coating is provided over the sub-coating.

-Prior to applying this additional coating or layer the article bearing the sub-coating is first washed, as in hot water.' In addition, it maybe immersed for relatively short times in a solution of chromic acid, particularly if chromic acid is not utilized in the sub-coating operation. If the it is desirable to dry the surfaces of the object 7 by any suitable means, such as a stream of air under pressure, dry steam, heat or the like.

In order to properly protectively coat ferrous metal objects according to the present method,

it is desirable that the surfaces to be coated not only be clean but that they be freed from prominent burrs or other irregularities which normally are produced by stamping or drawing operations. For the purpose of providing this desired surface a sand blasting operation may be employed. For

this purpose any conventional and suitable sand blasting apparatus or device'may be utilized. Sand itself may lie-employed as the medium therein as well as steel shot or other substances normally employed in sand blasting'operations.

After the sand blasting operation it is, of course, desirable that the surfaces be subjected to a further cleaning operation in orderto remove sand or other materials which may be presing' operation, or as a result of the handling operations necessary for carrying out said operation- .Any suitable cleaning operation may be utilized for those purposes, such for instance as one of the" emulsion type cleaners described in detail hereinbefore.

According to the present invention at least two coatings orlayers are disposed upon the surfaces of' the ferrous metal ice tray to be protected.

The first or innermost of these layers is referred to herein as the sub-coating. This sub-coating is produced by immersing the article in heated dilute solutions of phosphoric acid or phosphates, or submerglng it in similar solutions of chromates or chromic acid to produce an adherent coating on the surface consisting of iron phosphates or chromates. Processes of this general character are known and are practiced under a number -of names, such as "Bonderizing'j Granidizing and the Chromadine" process. The latter process may be carried out by immersing the ferrous metal object to be coated in a bath or solution containing chromic acid and sodium chloride. The former processes are fully explained in several United States Letters Patentamong which are-the following, reference to which is hereby made: Green et al. No.

1,651,694, Tanner and Darsey No. 1,888,189, and

Tanner andLodeesen No. 1,911,726. As a result ent on the surfaces as a result of the sand blastarticle bearing the sub-coating is placed in the chromic acid solution, as recommended, it is thereafter dried as by a blast of hot air, steam,

heat, compressed air or the like.

i The ferrous metal object bearing the sub coating is next provided with a protective coatingconsisting of a novel and improved resinous material; As more fully explainedhereinafter, the coating comprises polymerized or reacted alkyd resins, urea formaldehyde resins and melamine formaldehyde resins together with pigments. Furthermore, we have found it desirable to utilize at least two layers of this resinous material which,

for present purposes, we refer to as the "prime" coating and the finish coating.

In order to apply the present resinous coatings there is-prepared a coating bath or solution containing the resinous materials in their unreacted or in their partially reacted or partially polymerized or unpolymerized form, plus pigments and solvents. This bath or solution is then applied to the object as by dipping or spraying and is thereafter adhered to the object by air drying and also by baking as explained more fully hereinafter.

OF COA'I'ING BA'I'Id OR SOLUTION 170 Mm GALLONS Urea formaldehyde resins Approximately 12 to 100 Melamine formaldehyde resins Approximately 20 tol20 Solvents Pounds Benzol "Approximately 100 to 400 Xylol -c Approximately 100 to 400 Butanol Approximately 1 to 20 Hexyl alcohol Approximately .5to 15 Mineral spirits. "Approximately 0 to 100 The aforesaid ingredients may be varied within the above ranges provided, however, that the weight of all of the solvents combined should not greatly exceed 400 pounds.

Referring to specific substances. which may be utilized as the above ingredients and to equivalents therefor, we have found that one of thepigments should be titanium dioxide or zinc sulphide. The inert pigments referred to above may be any suitable pigments adapted to serve as a filler or binder, and many such pigments will ocour to one skilled in the art. Among them arebarium sulfate and silica. The pigment extender referred to above is utilized principally to prevent separation of the other pigments from the solution or bath, and to keep the entire pigment content in a finely divided and suspended condition. We recommend for this purpose the use of calcium carbonate and particularly that form of calcium carbonate referred to in the art as Multifiex." This is a speciall precipitated type of calcium carbonate bearing an electrical charg in solution.

Referring now to the resins mentioned in the above general formula, the urea formaldehyde resin and melamine formaldehyde resin are speciflc types of resins and therefore require no further explanation. The alkyd resins, of course, cover a relatively wide class of resins and we have found that numerous members of this class of resins may be employed. Weparticularly recommend, however, the use of a glycerol phthalate type of alkyd resin modified by a drying oil or a non-drying oil. In particular, we recommend as a drying oil modified glycerol phthalate resin, that a glycerol phthalate resin reacted with 'coc'onut oil be employed. In addition, we recommend that the formaldehyde resins (the urea formaldehyde plus the melamine formaldehyde resins) should be. used in, proportions such that not less than approximately 30 parts by weight of the total resin content are formaldehyde resins. The formaldehyde resins also may be used in amounts greater than approximately 30 parts by weight of the total resin content. alkyd resins function as plasticizers for the'formaldehyde resins; but whatever the explanation,

the use of both of these types of resins appears to be of importance in securing our improved protective coating.

Referring to the solvents mentioned in the above general formula, almost any combination Pigments Pounds Titanium dioxide (Rutile? type-freshly precipitated) 260 Barium sulfate 138 Calcium carbonate (Multifiex type) 77 Resins Pounds Drying oil modified glycerol phthalate resins 160 Non-drying oil modified glycerol phthalate resins 108 Urea formaldehyde resins 13 Melamine formaldehyde resins 48 Solvents Pounds Benzol 145 Xylol u 123 Butanol 20 Hexyl alcohol 13 Mineral spiri 97 'We believe that the cyclic type of organic solvents in the above gen- 4 eral formula are benzol and xylol. Turpentine is another cyclic type of solvent which may be used. As indicated by this general formula, these cyclic type compounds may be diluted by or mixed with other types of compounds, such as' the alcohols or mineral spirits mentioned. Other suitable organic solvents may be employed for this diluting or mixing process, if desired; We have found that the undiluted cyclic type of solvents By way of further explanation but not of limltation, one specific formula utilized for compounding the present coating solution or bath is as follows:

SPECIFIC COATING SOLUTION OR BATH While a suitable coating solution or bath made up in accordance with the foregoing disclosure '.may be utilized for either the prime or finish coating, we have found that certain changes for the finish coating appear to bede'sirable. In the finish coating solution it is desirable to decrease the proportion of inert pigments as compared with the proportion of such pigments contained in the prime coating solution. Also, the total pigment content of the finish coating solution should preferably be in the lower range of proportions given in the above general formula and should be less than the total pigment content in the prime coatingsolution.

In view of the foregoing, it is recommended that the inert pigment in the prime coating be approximately thirty eight pounds. Therefore, it will be seen that in the prime coating there is a relatively higher proportion of titanium oxide.

Also, it is desirable in the finish coating to utilize a relatively high proportion of resins to pigment. Still further, it is desirable that. the finish coating solution be somewhat thinner than the prime coating solution and therefore, the total solids, contained in the coating solution or bath should be approximately of the total weight of the coating solution or bath for the finish coating and approximately for the prime coating, although the latter percentage may i be increased to as high as The aforesaid coating solutions or baths W'ill provide an opaque. whi te coating resemblin enamel in appearancel By the simple expedient of-adding suitable colored pigments or other coloring agents the coating may be given any desired color. Many suitable coloring agents will occur to a skilled chemist. For instance, iron blacldwill produce -a black coating, chrome yellow a yellow coating, and various iron oxidepigments will produce red or brownish coatings.

A coating solution-or bath made up in accordance with the foregoing directions and formulas will possessapproximately the correct viscosity for applying the coating by a dipping operation.

where a. dippin coating. Also, such- I However, it is to be understood that this viscosity should be carefully regulated in order that the object .may be dipped or immersed in the coating solution or'bath with satisfactory results. Accordingly, a coating solutionmade up in accordance with these directions and formulas may be altered somewhat as to viscosityby the simple means of adding or taking away solvents, as the case may require. I have found that several.

factors should be: considered in regulating the viscosity of the solution or coating bath. Amon ject is treated at room temperature, and where the shape of the object is not unusual, I have found that the viscosity of the coating solution or bath for a dipping operation should be apis reasonably free from draughts, where the obproximately twenty to thirty seconds, when meas- H ured on a viscosimeter utilizing a number fourtip on a Ford cup.

If the coating solution or bath is to be applied to the object by a spraying operation,it is-recommended thatthe viscosity of thesolution be increased, that is, that the solution be heavier.

The factors mentioned above for determining the considering the viscosity for spraying application include the air pressure and assuming that a spraying boothis utilized, the rate of exhaust.

from the spraying booth. Since these factors vary considerably with each spraying 'operation,

it is not possible to provide herein exact viscosities for each and every spraying operation. However, one skilled in the art can easily determine the desired viscosity suitable for his particular conditions. As a rule, however, more high boiling solvents or a relatively larger concentration of high boiling solvents should be employed if a spraying operation is employed than method of application is employed. j

As indicated above, the coating solution or bath is applied to the object by immersion, dipping, spraying or other suitable means.- The amount of coating thus applied shouldbe sufficient to provide a film weight of the coating solution in 'viscosity for dipping also should be considered for a spraying operation. Additional factors in plished by subjecting the object to increased temperatures. Approximately fifteen minutes at temperatures of from3fi0 to 375 F. have been -found,to suffice as have approximately 11 minutes at about 400 F.

Any suitable apparatus for air drying and baking the coating may be utilized although it is preferable that the air drying operation immediately precede the baking operation, and that the temperatures during the air drying operation be gradually increased duringthat operation until they approach the minimum tempera- 4 ture of the baking operation. In this connection one suitable form of apparatus for effecting the air drying and baking operation of the-pres ent coating is disclosed and claimed in our U. S.

Letters Patent No. 2,375,173.

It'will be understood, however, that but one coating may be utilized if desired and that more than two coatings also may be utilized, although we have found. that a prime and a finish coating appears to produce satisfactory results.

An ice tray coated in accordance with the present inuention possesses on its surfaces a subcoating consisting of reaction products of the ferrous metal and the phosphates or chromates utilized in applying the sub-coating. Over this sub-coating the article possesses a prime and finish coating consisting of reaction or polymerization products of the alkyd resins, urea formaldehyde resins and melamine formaldehyde resins utilized as ingredients ,in the coating solution or bath. In addition, these prime finish coatings contain pigments, particularly titanium; dioxide. It is our belief thatthese pigments are not simply present in the finish coating as unreacted particles within the polymerized or reaction'products of the resins. Apparently said pigments enter the'reaction itself which produces the polymerized and reaction, product coating.

At'- least they appear to provide focal points about whichthe polymerizing or reacting of the resins takes place. However, these observations mere ly represent our opinion in this respect. Whatever the chemical explanation, the pres- -.ent'novel coating provides an exceptionally effective corrosion and rust resistant coating which is particularly satisfactory for ferrous metal ob- -.j ects which are subjected to rigorous'conditions.

an amount ofapproximatelytwoto three millirams per square centimeter. This is regarded as a minimum in order'that the present coating mayoperate effectively. Thinner coatings appear to suflice to provide a corrosion and rust resistant coating, but such thinner coatings usually do not havesufficient hiding power to provide a pleasingly ppearing and wholly satisfactory thin coatings tend. to be removed too easily by mechanical abrasion. It

is,'therefore, desirable to utilize more than this minimum. It is recommended thatfrom live to nine milligrams per square centimeter'be employed. In fact, we have utilized as much as twelve to fifteen milligrams per square centimeter althougl nthese heavy coatings do not appear-,to add to the protective properties of the coating.

However, such heavy coatings could, of course, be employed. After the object has been air dried;

- it is-baked. This baking operation is accomously"aifecting the coating.

In particular, this coating is sufliciently'flexlble that it'does not chip or is not otherwise removed from the article, even-if the article isflexed or bent. 'Thus, the article may be relatively roughly handled without deleterious effects. An ice tray bearing the present coating may be removed from and placed in the refrigerator and may be roughly. handled to remove theice cubes without deleteripresent coating is sufliciently resistant to abrasion so that it is not ea'silyscraped from the coated ob- .l'ect. Therefore, an ice tray bearing the present coating may have a grid placed in it and may have said grid removed byprying, when necessary, to

remove the ice'cubes without breaking down the coating. Still further, ice or frozen materials do not adhere firmly tothe present coating thus facilitating the removalof such materials.

The present coating is pleasing in appearance,

does not react with rubber or the like so that rubber grids or inserts may be employed without producing black marks'or other unsightly or deleterious effects, and may be safely'used with edible products" without in any way tainting them or affecting their taste. Therefore, lce trays or similar 'objects'bearing the; presentcoatlng may be Furthermore, the

satisfactorily employed for the purposes for which they were intended.

We claim:

1. A ferrous metal ice tray for receiving materials to be frozen, said tray possessing on its material contacting surfaces an adherent protective coating comprising an iron phosphate and thereover a moisture repellent baked enamel-like flexible, adherent and abrasion resistant layer containing titanium dioxide and the combined polymerization products of an alkyd resin, a urea formaldehyde resin and a melamine formaldehyde resin.

2. A ferrous metal ice tray for receiving materials to be frozen, said tray possessing on its ma.- terial contacting surfaces an adherent protective coating comprising an iron phosphate and thereover a baked enamel-like layer containing pigments including titanium dioxide and polymerization products of approximately 60 to 120 parts by weight of alkyd resins, approximately 12 parts -to 100 parts by weight of urea formaldehyde resins and approximately 20 to approximately 120 parts by weight of melamine formaldehyde resins.

3. A ferrous metal ice tray for receiving materials to be frozen, said tray possessing on its material contacting surfaces, an adherent protective coating comprising an iron phosphate and thereover a flexible, adherent, moisture repellent and abrasion resistant baked enamel-like layer containing pigments including titanium dioxide and containing the combined polymerization products of a dryingoil modified glycerol phthalate resin. at non-drying oil modified glycerol phthalate resin, 2. urea formaldehyde resin and a melamine formaldehyde resin.

4. A ferrous metal ice tray for receiving materials to be frozen, said tray possessing on its material contacting surfaces an adherent protective coating comprising an iron phosphate and thereover a flexible, adherent, moisture repellent and abrasion resistant baked enamel-like layer containing pigments including titanium dioxide and polymerization products of approximately parts by weight of a drying oilmodified glycerol phthalate resin, approximately 108 parts by weight of a non-drying oil modified glycerol phtha-late resin, approximately 13 parts by weight of a urea formaldehyde resin and approximately 48 parts by weight of a melamine formaldehyde resin. ALBERT L. BUNTING. ARTHUR C. SCHULTZ. 

